I had posted on endless sphere but since then I have possibly made a little discovery.

Tldr; I have a fresh 48v battery and charger around less than 3 months old. Very intermittently when trying to charge the battery the charger will power up, the fan spins up and then it starts to make a nasty buzzing / whirring sound. Its pretty loud normally but this is something else.

My discovery since the last post is that I no longer believe this is a broken fan issue, as I know that can make a lot of noise. I will not dismiss the possibility by any means though. Main reason for believing this is that when I charge at home it boots up fine and lightly whirrs. But more often than not I have noticed when I am charging in my place of work, this weird sound starts like clockwork almost as soon as I turn it on.

I can be entirely sure of this but id say i cant remember it once doing it at home, but its happened around 10 times now in work. Sometimes it can charge fine even on the supply, it is kind of odd.

I have attached a picture of the charger and a video sample of the noise it makes.

It is a generic style chinese brand charger so criticise if you wish but this is brand new, CE and RoHS tested.

Any help or SUGGESTIONS FOR A NEW CHARGER using the bespoke connector it has would be GREATLY appreciated.

The charger is a generic-style C300 model battery charger, similar to the one shown below: enter image description here

[Charger noise video] https://streamable.com/1kmpr

[3 Pin DIN style connector, not XLR] enter image description here

  • 1
    3 months, this is rather a warranty issue. Consult your dealer ASAP.
    – Carel
    Commented Jan 15, 2020 at 13:18
  • If all else fails splice the old connector onto the new cable. Commented Jan 15, 2020 at 14:16
  • Just to be clear, is the clicking in that video from the charger itself or from you turning it on and off? Assuming the former, something is tripping and restarting. Do other devices work the same on both outlets? If you can find an incandescent lamp is it the same brightness on both?
    – Chris H
    Commented Jan 15, 2020 at 16:11
  • 1
    Oh, and stupid question: Did you check around the fan to see if a piece of trash may have fallen in there? Commented Jan 15, 2020 at 17:12
  • @ChrisH Yes the clicking is me, I'm turning it off because I don't like to leave it in that state too long, seems damaging perhaps but maybe not.
    – Jpotts12
    Commented Jan 15, 2020 at 22:31

4 Answers 4


Even though the design may be CE compliant, the unfortunate reality is that cheap manufacturers will still leave out "unnecessary" circuit components or replace them with fake ones when actually building it. (RoHS just means it's free of lead and mercury etc etc, nothing to do with quality or usability of the electrical design.)

The components that are supposed to filter and reject electromagnetic noise are common victims since they're both expensive and it "normally" works just fine without them.

So if it works fine at home but makes weird noises at work, it seems more likely there's a failing connection in the electrical power system at your work putting a lot of noise on the line, rather than a problem with your charger. (Other than potentially failing to reject an amount of noise that other DC supplies in the building seem to be handling, whether due to a lazy design or corners being cut in assembly.)

  • correct yes a lot of manufcaturers are cheap with their CE compliance and find as many ways to cut costs asides the main components, really disappointing. Frey ebike are fairly reputable company but this charger is off brand generic so wouldnt surprise me.
    – Jpotts12
    Commented Jan 18, 2020 at 2:54
  • @affe would there be a way to add the 'noise filtering' in between the outlet at his place of work and the charger itself?(to be able to keep using the existing charger?) Commented Jan 20, 2020 at 0:58
  • If that is the root problem it's a potential fire hazard in the building and they should be doing something about it, not mitigating it on the decide side! Didn't want to get into all that not knowing what OP's location is and it getting pretty far off topic. (But yes there are some types of devices you can find with a google for 'AC Line Filter' or 'Power Line Filter' if the problem is in some way 'legitimate' (like the panel is shared with a machine shop or something...I dunno...?) and not an arcing fault or ground leak.)
    – Affe
    Commented Jan 20, 2020 at 16:15
  • Hi, I will be mentioning these comments to some engineers in our building thanks to you, just in case of course. We are based in quite a large 4 floor building with duplicated sockets almost every few metres in some places along these conduits that run the length of the walls. Lots of pc equipment etc so lots of separate lines, can see where they might run into interference problems but I don't know a whole lot, will pass the comments on thanks to you guys x-) you learn something new everyday, its ‘essentially’ the building and not the charger 😂 Although the manufacturers have cheaped out..
    – Jpotts12
    Commented Jan 23, 2020 at 14:58

That sounds just like a normal high speed fan in a charger to me. My charger has one and sounds like that when charging, stops when battery is charged even when still connected.

  • 1
    Welcome to Bicycles SE. This site does not operate like a typical forum. It operates on a Q&A basis. Please only use the "answer" button to answer the OP's question. Once you have asked and answered a few questions, you'll have earned enough reputation to comment everywhere on the site.
    – Ted Hohl
    Commented Jul 24, 2023 at 13:25
  • Welcome to the site - OP confirmed in comments that the wall socket used at work was "strange" and the charger worked fine on other sockets. This noise was definitely not normal.
    – Criggie
    Commented Jul 25, 2023 at 21:08

I would think that the different outlets are just a red herring. The loud unhealthy noise that broken fans make is actually coming from the fan's bearings. In effect, that fan's axis is dancing around withing the play of the bearing, creating the gruesome noise, producing heat, and damaging the bearing further.

Now, bearings are frequently lubricated, and the viscosity of the lubricant depends on environmental factors. Most notorious is the temperature of the bearing itself, but also humidity may play a part.

When you use your charger at work, the charger is likely at quite a different temperature (for instance by being transported on the bike) than when you charge your battery at home, and that may trip the bearing into dancing.


It may be miswired plug.

If the plug of the charger contains three terminals, it may be incorrectly wired, by swapping ground and neutral. This is a dangerous configuration to use that also may or may not work, depending on what the installation does with the ground wire. Ground and neutral wires should not actually be connected right at the socket or nearby, but they are often connected at the final step-down transformer of the supply. Some particular socket may not have ground connected at all so this explains why the wrongly wired plug works on some sockets and not others.

It may be the case if the plug has been manually replaced, cutting away a plug from one country and screwing on a different plug for another.

If the power cable of the charger can be disconnected from the charger and there is a replacement at hand, I would suggest to try with another cable.

While in the simplest case ground and neutral are simply connected together at the system neutral point, it may be more complex safety devices installed there that could interfere with the voltage converter of the battery charger, causing it overheat, produce the excess noise or simply prevent from working.

  • 1
    The plug works in one location but not in another. It is, however, possible that the socket was miswired at one or the other location. You can get socket testers to tell you if the mains / neutral / ground were miswired. Commented Feb 16 at 16:28

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